Surface texturization of material is well known and is employed for a variety of purposes. In the manufacture of integrated circuits removal of portions of a crystalline surface by etching is common as shown, for example, in U.S. Pat. No. 3,765,969. The idea of damaging the surface as by mechanical means or by use of radiation before etching to enhance the etching process also is known as shown in U.S. Pat. Nos. 3,041,226, 3,801,390, and 3,808,068. However, these patents involve isotropic (dissolution) etches, not anisotropic etching for surface texturization. The use of radioactive material for bombarding a plastic sheet to form radiation damage tracks therein which subsequently are etched through the material to form a filter, and not for surface texturization, is shown in U.S. Pat. No. 3,713,921. Additionally, the surface texturization by mechanical damage and etching of the light-incident surface of a silicon substrate included in a solar cell to reduce reflectance is known as disclosed in articles entitled, `Optical Properties of the COMSAT Non-Reflective Cell` by R. A. Arndt, J. F. Allison, J. G. Haynos and A. Meulenberg, Jr., and `V-Grooved Silicon Solar Cells` by C. R. Baraona and H. W. Brandhorst, pages 40-43 and 44-48, respectively, of Proc. 11th Photovoltaics Specialists Conf., Scottsdale, Ariz., May 6-8, 1975.
Major disadvantages of photovoltaic, or solar, cells have been the high cost and the low efficiency thereof. Surface texturization of the light-incident silicon surface of solar cells to reduce reflectivity, thereby improving efficiency, has to date involved processes which are costly and/or which do not result in a uniform texturization of the surface as is required for maximum efficiency. In use, thousands of solar cells may be interconnected to provide the necessary power output. With ever-larger diameter crystalline substrates the number of cells required to produce the same output is greatly reduced. However, the increased size of the cells contributes to the difficulty of uniformly texturizing the cell surface. By use of the present texturization process of our invention, large surface areas are uniformly texturized in a controlled manner at a high rate and minimum cost.